The technique relating to OFDM (Orthogonal Frequency Division Multiplex) modulation and demodulation and the technique relating to modulation and demodulation with the unitary matrix are conventionally disclosed in the following documents.    [Patent Document 1] Unexamined Japanese Patent Publication No. 2002-185428    [Patent Document 2] Unexamined Japanese Patent Publication No. 2001-285242    [Patent Document 3] Unexamined Patent Publication Hei. No. 10-107761    [Non-Patent Document 1] Chang-Jun Ahn and Iwao Sasase, “Convolutional Coded Coherent and Differential Unitary Space-Time Modulated OFDM with Bit Interleaving for Multiple Antennas system”, Shingakugiho, TECHNICAL REPORT OF IEICE, SST2002-47, October, 2002, pp. 75 to 80
The Patent document 1 discloses an invention relating to an OFDM communication system.
Particularly, this discloses a system in which a received OFDM signal is transformed to frequency-domain components by a fast Fourier transform, the frequency-domain components are processed to timing components, timing information is derived from the timing components, and timing information is applied to the received OFDM signal to be synchronize with a receiver.
The patent document 2 discloses an invention relating to an OFDM demodulation apparatus that receives a PSK signal, which is sent by OFDM modulation to transmit information using phase components, and that performs soft decision decoding of this signal.
Particularly, there is disclosed the method relating to a con on in which a filter property of a band limiting filter that cuts off out-of-band components from a received signal is detected an output signal of the band limiting filter is converted to a phase signal, thereafter the phase signal is corrected according to the lifter property and soft decision decoding is performed.
The patent document 3 discloses an invention relating to a coding transmission system and a transmitter and a receiver based on an OFDM method.
Especially, this discloses the invention relating to a configuration in which an OFDM received signal is subjected to OFDM demodulation and demapping, the OFDM modulated signal is subjected to inner deinterleaving by an inner deinterleave circuit, an OFDM decoded signal subjected to inner deinterleaving is further subjected to inner coding and decoding by an inner demodulation circuit the inner coded and decoded signal is subjected to outer deinterleaving by an outer deinterleave circuit, and the inner coded and decoded signal subjected to outer deinterleaving is further subjected to outer coding and decoding by an outer coding and decoding circuit to output a result.
The non-patent document 1 is a paper on the past study in which one of the inventors of the present application joined, and discloses an invention in which modulation and demodulation in space and time are performed using unitary matrixes and a plurality of antennas is used to emit a signal with a time difference.
However, various kinds of communication techniques applicable to the OFDM communication other than the aforementioned techniques have been strongly desired.
The present invention has been made to solve the aforementioned problems and an object of the present invention is to provide a transmitter, receiver, transmitting method, and receiving method that perform efficient communication using modulation and demodulation with a unitary matrix where elements excepting diagonal elements are zero by use of a LDPC code, and program for implementing these on a computer.